1. Field of the Invention
The present invention relates generally to the field of aerial spraying equipment, and more particularly, is directed to an improved spray nozzle, particularly designed to prevent the dribbling of liquid chemicals upon completion of a spray run.
2. Background Information
In order to economically control weeds and other undesirable growths, it is now the common practice to utilize known systemic herbicides and specifically designed delivery systems such as aircraft which have been modified as necessary for agricultural use. When applying systemic herbicides, especially when employing aircraft, it is well known that only a few droplets of the systemic herbicide will be sufficient to kill a plant. Because of this, it is most important that the herbicides be directed precisely upon the target area and that care be taken to prevent drift and dribble of the material. Frequently, when the spraying operations cannot be adequately controlled, the systemic herbicides will attack economic crops and other agricultural growths which are not intended or desired to be removed. This is caused when the material being sprayed accidentally falls in a non-designated area such as may be occasioned by crosswinds, drafts and similar atmospheric conditions which might cause the herbicide droplets to be carried to the unwanted areas.
In order to reduce the damage caused by the drift of systemic herbicides, prior workers in the art have attempted to develop various chemical and mechanical means to increase droplet control and thereby decrease damage to valuable plant life. One previously utilized system involves the employment of a heavy invert herbicide emulsion to produce only large, heavy droplets during the spraying operations. In theory, the large, heavy droplets will be so large and so heavy that they will remain substantially unaffected by crosswinds and drafts during the application procedures. Because of this, the application of the herbicide to the designated area will be quite accurate and will be substantially unaffected by atmospheric conditions. While some success has been experienced when applying heavy invert emulsions, the use of such heavy invert emulsions has required added equipment costs and increased time factors, the combination of which have resulted in economic conditions which are so burdensome as to render the system to be only marginally successful.
In U.S. Pat. No. 3,445,065, the present applicant has invented and disclosed a uniform droplet discharge sprayer for use with aircraft. The uniform droplet sprayer employs a plurality of rearwardly extending, parallel nozzles appropriately connected to a transverse discharge line or boom through spring loaded hydraulic valves. The hydraulic valves were especially provided to control dribble from the nozzles following shut-off of the supply valve. In one embodiment, a sponge-like material was utilized to retain the liquid herbicides within the sprayer construction. The prior sprayer comprised a generally elliptical body section in airfoil form, having a single inlet, and a plurality of closely spaced nozzles connected to each sprayer. It has been found that when the sprayers disclosed in U.S. Pat. No. 3,445,065 were utilized for the aerial application of systemic herbicides, problems in dribble could develop if the liquid input to the sprayers was shut off while the aircraft was making a turn. The normal banking during turning of the aircraft caused the nozzles at one end of each sprayer to be elevated as much as one inch above the lowest nozzles at the opposite end of the sprayer. This differential in elevation and consequently in pressure could be sufficient to cause the top nozzle or nozzles of each sprayer to suck in air thereby simultaneously causing dribble from the lower nozzle or nozzles of each sprayer.
Similarly, in U.S. Pat. No. 3,523,646, the present applicant disclosed a plurality of sprayers supported upon the spray boom of a helicopter wherein each sprayer comprised a single inlet and a plurality of closely spaced discharge nozzles trailing from each sprayer. To accommodate the number of discharge nozzles required for adequate application purposes, each sprayer had to be constructed to be at least approximately six inches in length. Again, upon completion of a herbicide spraying run, and upon closing of the shut-off valve, some of the material remaining within the sprayers would be caused to dribble out and fall to the ground as the aircraft banked when making a turn, thus causing the discharge nozzles at one end of each sprayer to be elevated above the discharge nozzles at the lower end of the sprayer. The banking of the aircraft could cause as much as a one inch elevation differential between the lowermost discharge nozzle and the uppermost discharge nozzle of each sprayer. This differential could cause the top or uppermost discharge nozzles to suck in air and the bottom or lowermost discharge nozzles to dribble herbicide, thereby causing unwanted trailing and possible damage to crops or other plants in adjacent fields.
Accordingly, the need remains to provide an improved herbicides discharge nozzle construction that is capable of eliminating all dribbling upon completion of each spray run to thereby positively control the spray pattern, to prevent trailing and to prevent damage to adjacent areas.